1. Technical Field
The present invention relates to a mechanism and a method for automatically changing tools, and more particularly to such an automatic tool changing mechanism and method suitable for application to an apparatus in which a spindle and a tool magazine are rotated by a single spindle motor.
2. Discussion of the Prior Art
Automatic tool changing (hereinafter referred to as "ATC") functions are capable of automatically detaching a tool from a spindle and mounting a new tool on the spindle without manual intervention based on a tool change command, there being included a tool magazine storing a plurality of tools. A conventional ATC apparatus with such an ATC function has a complex mechanism for rotating the tool magazine to index to a desired new tool. An ATC apparatus as shown in U.S. Pat. No. 4,053,251, for example, converts movement of a spindle mechanism along a Z-axis into intermittent rotation of a tool magazine for changing tools. However, such a construction is complicated, and it takes a long period of time for tools to be changed as one reciprocating motion of the spindle mechanism in the direction of the Z-axis corresponds only to an angular displacement of the tool magazine for a single tool pitch.
There is another ATC apparatus in which a tool magazine is rotated by a separate motor for a tool changing operation. This apparatus however is large in size and costly to construct.